Cable

Abstract

The invention provides a multi-core cable which is easy to bend, and the shape of the multi-core cable is easy to maintain in a bent state. A cable (1) is provided with a plurality of electric wires (2) having an insulator (22) covering the periphery of a conductor (21), and a sheath (7) covering the periphery of an integrated core (4) formed by twisting the plurality of electric wires (2) in two or more layers, the adjacent electric wires (2) in the integrated core (4) are in contact with each other on the surface of the insulator (4), and the insulator (22) has a surface roughness (Sdr) of 1.0 or more and a surface roughness (Spc) of 3000 mm-1 or more.

Description

Technical Field

[0001] The present invention relates to cables. Background Art

[0002] In devices such as industrial robots that use multiple wires, multiple cables are combined into one cable in order to reduce weight and improve handling. Therefore, in recent years, multi-core cables formed by covering multiple wires with a sheath have been widely used. It should be noted that as prior art document information related to the present invention, there is Patent Document 1.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-73741 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, in the multi-core cable using multiple electric wires as described above, the outer diameter becomes larger and the cable is difficult to bend. In addition, in the multi-core cable using multiple electric wires as described above, the resilience of the cable to return to a straight state when it is bent becomes too high, and there is a problem that it is difficult to maintain the cable in a bent state. For example, when wiring the cable, it is necessary to carry the cable in a state of being wound with a small bending radius, but in a cable with too high resilience, it is difficult to be wound with a small bending radius, and the workability during wiring and the degree of freedom of wiring layout will be reduced.

[0008] Therefore, an object of the present invention is to provide a multi-core cable that is easy to bend and easy to maintain its shape in a bent state.

[0009] Methods for solving problems

[0010] The present invention aims to solve the above-mentioned problems and provides a cable comprising a plurality of electric wires having an insulator covering the periphery of a conductor and a sheath covering the periphery of a core assembly formed by twisting the plurality of electric wires in two or more layers, wherein the electric wires adjacent to each other in the core assembly are in contact with each other on the surface of the insulator, and the surface roughness Sdr of the insulator is 1.0 or more and the surface roughness Spc is 3000 mm. -1 above.

[0011] Effects of the Invention

[0012] According to the present invention, it is possible to provide a multi-core cable that is easy to bend and easy to maintain its shape in a bent state. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1This is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of a cable according to an embodiment of the present invention.

[0014] Figure 2 In the drawings, (a) is a microscopic photograph of the surface of the insulator in the electric wire of the example, and (b) is a microscopic photograph of the surface of the insulator in the electric wire of the comparative example.

[0015] Figure 3 It is a graph showing the measurement results of the deflection amount.

[0016] Explanation of symbols

[0017] 1…cable, 2…wire, 21…conductor, 22…insulator, 3…central clamping member, 4…collective core, 5…binding layer, 6…shielding layer, 7…sheath. DETAILED DESCRIPTION

[0018] [Implementation Method]

[0019] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0020] Figure 1 1 is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of the cable 1 according to the present embodiment. The cable 1 is used, for example, as wiring to connect an industrial robot and a control panel.

[0021] The cable 1 includes a plurality of electric wires 2 , a bonding layer 5 disposed around a core assembly 4 formed by twisting the plurality of electric wires 2 in two or more layers, a shield layer 6 formed of a braided shield disposed around the bonding layer 5 , and a sheath 7 covering the shield layer 6 .

[0022] (Wire 2)

[0023] The electric wire 2 is an insulated electric wire having a conductor 21 and an insulator 22 covering the conductor 21. The conductor 21 is composed of a stranded wire in which a plurality of metal wires are stranded together. The metal wire is made of copper or a copper alloy. It should be noted that a wire made of aluminum or an aluminum alloy may also be used as the metal wire.

[0024] If the insulator 22 is hard, the contact area between the adjacent wires 2 becomes smaller, and the wires 2 are easy to move relative to each other in the length direction, and the cable 1 is easy to bend. However, if the insulator 22 is hard, the resilience to restore it to a straight state becomes high, and it is difficult to maintain the cable 1 in a bent state. On the other hand, if the insulator 22 is made soft, although the resilience is reduced and it is easy to maintain the cable 1 in a bent state, since the contact area of ​​the adjacent wires 2 at the part where the insulator 22 contacts each other becomes large, it is difficult for the wires 2 to move relative to each other, and it is difficult to bend the cable 1. Therefore, in this embodiment, as the insulator 22, a softer material is used to easily maintain the cable 1 in a bent state, and the outer peripheral surface of the insulator 22 is made into a predetermined surface roughness so that it is easy to slide, so that the wires 2 are easy to move relative to each other, and the cable 1 is easy to bend.

[0025] More specifically, in the cable 1 of the present embodiment, the surface roughness Sdr of the insulator 22 constituting the electric wire 2 is 1.0 or more and the surface roughness Spc is 3000 mm. -1 Above. It should be noted that the surface roughness Sdr is the ratio of the surface area to the area of ​​the measurement area, also known as the expansion area ratio of the interface. The larger the surface roughness Sdr, the greater the inclination of the surface concave and convex. In addition, the surface roughness Spc is the arithmetic mean of the curvature of the convex part of the surface, also known as the arithmetic mean curvature of the peak vertex. The larger the surface roughness Spc, the sharper the front end of the convex part. The determination methods of these surface roughness Sdr and Spc are as specified in ISO 25178.

[0026] By setting the surface roughness Sdr of the insulator 22 to 1.0 or more and the surface roughness Spc to 3000 mm -1 As described above, a plurality of fine concavoconvexities are formed on the surface of the insulator 22, so that the surface contact area of ​​the insulator 22 when the wires 2 are in contact with each other on the surface of the insulator 22 can be reduced, and the friction force can be reduced. As a result, even if the wires 2 are arranged in close contact, the wires 2 are easy to move relative to each other in the length direction, and the cable 1 is easy to bend. In particular, in a state where the cable 1 is not bent, even if a plurality of wires 2 are in close contact with each other in a surface contact state on the surface of the insulator 22, the cable 1 can be easily bent. The surface roughness of the insulator 22 can be adjusted appropriately by adjusting the manufacturing conditions such as the temperature during extrusion molding, the amount of plasticizer used for the insulator 22, and the adjustment of additives. It should be noted that the arithmetic mean roughness Sa of the insulator 22 can be greater than 1.5 μm and less than 3.0 μm, and more preferably greater than 1.7 μm and less than 2.7 μm.

[0027] In addition, the Shore A hardness of the insulator 22 can be 77 or more and 93 or less. By setting the Shore A hardness of the insulator 22 to 77 or more, the insulator 22 will not be too soft, so it is possible to prevent the twisted multiple wires 2 from being excessively flattened. By preventing the wires 2 from being excessively flattened, it is easy to obtain the above-mentioned effect brought about by making the surface of the insulator 22 in contact with each other to the specified surface roughness Sdr and Spc. In addition, by setting the Shore A hardness of the insulator 22 to 93 or less, the insulator 22 will not become too hard, so it is possible to prevent the force of mutual repulsion in the parts where the twisted multiple wires 2 are in contact with each other from becoming stronger. As a result, when the cable 1 is bent or wired, it is easy to maintain the bent shape (that is, it is not easy to naturally return to a state close to a straight line from a bent state). It is more preferred that the Shore A hardness of the insulator 22 is 80 or more and 90 or less, and it is further preferred that it is 85 or more and 90 or less. In this embodiment, as the insulator 22, a resin composition containing PVC (polyvinyl chloride) resin as a base resin is used. It should be noted that the Shore A hardness of the insulator 22 can be measured by a durometer hardness test method (Type A) in accordance with JIS K7125.

[0028] (Collection Core 4)

[0029] The core assembly 4 is formed by twisting a plurality of electric wires 2 in two or more layers around a central clamping member 3 provided in the center of the cable. Here, 8, 14, and 20 electric wires 2 are twisted in order from the radial inside, and a three-layer structured core assembly 4 is formed using 42 electric wires 2. Here, the case where all 42 electric wires 2 have the same structure is shown, but the core assembly 4 may also include electric wires 2 having different structures such as outer diameters. It should be noted that the total number of electric wires 2 constituting the core assembly 4 is, for example, 20 or more.

[0030] In order to concentrate stress on the center of the cable when the cable 1 is bent, it is preferred not to arrange the electric wire 2 at the center of the cable, and it is preferred to use a center clamping member 3. In the cross section perpendicular to the length direction of the cable 1, the cross-sectional area of ​​the center clamping member 3 can be larger than the cross-sectional area of ​​one electric wire 2. As a result, the stress concentrated on the center of the cable when the cable 1 is bent is not easily applied to the plurality of electric wires 2 constituting the layer closest to the center clamping member 3. In the present embodiment, as the center clamping member 3, a fiber clamping member composed of artificial fiber (rayon) is used. However, it is not limited to this, and a fiber clamping member composed of a material other than artificial fiber can also be used. For example, a solid linear body composed of only an insulator 22 other than the conductor 21 can also be used as the center clamping member 3 in the electric wire 2. As a result, for example, the outer diameter of the linear body can be made consistent with that of the electric wire 2, and the handling during manufacturing and the design of the outer diameter of the cable can be easily performed. In addition, as the center clamping member 3 arranged in the center of the cable, for example, a hollow tube can also be used. The tube used for the center sandwiching member 3 is made of a resin such as polyvinyl chloride resin or nylon. As a result, when the cable 1 is bent, the arrangement of the electric wires 2 is not easily disturbed and the cable 1 can be easily bent. It should be noted that a coating layer made of fibers such as rayon or a coating layer made of resin such as polyvinyl chloride resin can be provided in a manner covering the periphery of the tube. The coating layer provided around the center sandwiching member 3 formed of the tube can serve as a buffer layer between the center sandwiching member 3 and the electric wires 2 when the cable 1 is bent.

[0031] In order to easily maintain the cross-sectional shape of the cable 1 when the cable 1 is bent, the core assembly 4 may also be provided with a solid or tube-shaped intervening member between the wires 2 arranged along the circumferential direction of the cable. The intervening member arranged between the wires 2 is made of a resin such as polyvinyl chloride or polyurethane, and its outer diameter may be 0.9 times or more and 1.1 times or less of the outer diameter of the wire 2.

[0032] It is preferred that the twisting direction of the plurality of electric wires 2 constituting the collective core 4 is the same in all layers. As a result, the cable 1 is easier to bend and easier to maintain in a bent state. For example, when the twisting directions of the electric wires 2 are different in adjacent layers and the twisting directions are alternated, repulsion is generated between the layers, and the cable 1 is slightly difficult to bend. In addition, the cable 1 has a higher resilience to return to a straight line, and it is difficult to maintain in a bent state. It should be noted that the twisting direction of the electric wires 2 of each layer is the direction in which the electric wires 2 rotate from one end to the other end when viewed from one end of the cable 1.

[0033] (Binding layer 5)

[0034] The tie layer 5 is provided around the core assembly 4 and in contact with the outer peripheral surface of the core assembly 4. The tie layer 5 is a layer that plays a role in preventing the twist of the core assembly 4 from being untied, and is formed by spirally winding a tape member around the core assembly 4.

[0035] In the present embodiment, the cable 1 has a shielding layer 6 formed of a braided shielding member, so in order to suppress the fastening of the shielding layer 6 to the collective core 4 and maintain the bendability of the cable 1, a belt member with cushioning properties can be used as a belt member used in the bonding layer 5. Specifically, as a belt member for the bonding layer 5, a foamed belt having a foamed layer formed of a foamed resin or a non-woven belt can be used. In particular, when a foamed belt is used as a belt member for the bonding layer 5, the cushioning effect can be improved compared to a non-woven belt. Therefore, by forming the bonding layer 5 with a belt member and the belt member with a foamed belt, the cable 1 can be easily bent compared to a case where the bonding layer 5 is formed with a belt member and the belt member with a non-woven belt.

[0036] As the foaming tape, a tape made of foamed polypropylene that is difficult to flatten can be used. It should be noted that the foaming tape may not be a foam layer as a whole, but may be a structure in which non-foamed layers and foamed layers are stacked, or may be a structure in which foamed layers with different foaming degrees are stacked. By setting the foaming tape as a multi-layer structure, the cushioning property of the bonding layer 5 can be adjusted. Thus, the bendability of the cable 1 can be adjusted by the bonding layer 5. In addition, in the present embodiment, the bonding layer 5 is set as one layer, but a plurality of bonding layers 5 may be provided between the collective core 4 and the shielding layer 6. In the case of providing a plurality of bonding layers 5, a structure in which a bonding layer 5 formed by extruding and coating a resin formed by foamed polypropylene is provided around the bonding layer 5 formed by the foaming tape (which is formed by foamed polypropylene) may be adopted.

[0037] The winding direction of the tape member in the bonding layer 5 is set to a direction different from the twisting direction of the electric wires 2 in the core assembly 4. As a result, the arrangement of the electric wires 2 in the core assembly 4 can be maintained without deformation. However, in this case, the bendability of the cable 1 is slightly impaired, so in particular, in the cable 1 that requires bendability, the winding direction of the tape member in the bonding layer 5 can be set to the same direction as the twisting direction of the electric wires 2 in the core assembly 4. It should be noted that the winding direction of the tape member is the direction in which the tape member rotates from one end to the other end when viewed from one end of the cable 1.

[0038] (Shielding layer 6)

[0039] The shielding layer 6 is composed of a braided shielding member formed by braiding a plurality of metal wires. As the metal wire used for the shielding layer 6, a material composed of copper, copper alloy, aluminum or aluminum alloy can be used. In the present embodiment, the bonding layer 5 as the base of the shielding layer 6 plays a role as a cushion layer, so that the stress applied to the shielding layer 6 and the collective core 4 when the cable 1 is bent can be alleviated. As a result, the disconnection of the metal wire of the shielding layer 6 can be suppressed, and the damage of the electric wire 2 constituting the collective core 4 can be suppressed. It should be noted that the shielding layer 6 can also be omitted depending on the use purpose of the cable 1, etc.

[0040] (Sheath 7)

[0041] The sheath 7 is made of, for example, PVC (polyvinyl chloride) or the like. In the present embodiment, since the core assembly 4 includes a plurality of electric wires 2 such as 42 wires, the outer diameter of the sheath 7, that is, the outer diameter of the cable 1, is as large as 15 mm or more. Thus, in a thick cable 1 having an outer diameter of 15 mm or more, especially an outer diameter of 20 mm or more, the above-mentioned problems (problems such as difficulty in bending and difficulty in maintaining a bent state) are likely to occur, and the above-mentioned effects brought about by making the insulator 22 have the prescribed surface roughness Sdr and Spc are easily obtained. That is, the present embodiment is particularly suitable for cables 1 having an outer diameter of 15 mm or more, especially an outer diameter of 20 mm or more.

[0042] (Verification of surface roughness)

[0043] Directly above the conductor 21, an insulator 22 is formed by extrusion coating a resin composition containing a polyvinyl chloride resin as a base resin, and the electric wire 2 of the embodiment and the comparative example is produced. In the embodiment and the comparative example, the surface properties of the insulator 22 are appropriately adjusted by adjusting the amount of plasticizer and additives in the resin composition, and the surface roughness of the insulator 22 is measured. Here, the surface roughness is measured twice in both the embodiment and the comparative example. In addition, as the surface roughness, the arithmetic mean roughness Sa, the developed area ratio Sdr of the interface, and the arithmetic mean curvature Spc of the peak vertex are measured. The results are summarized in Table 1. In addition, microscopic photographs of the surfaces of the insulators 22 of the embodiments and the comparative examples are shown in Table 1. Figure 2 (a) and (b) The surface roughness of the insulator 22 was measured using a laser microscope (VK-X3000, manufactured by KEYENCE Co., Ltd.). Figure 2 The surface roughness of the entire surface of the insulator 22 shown in (a) and (b) (the measurement area is about 540 μm in the longitudinal direction and about 720 μm in the lateral direction) was measured.

[0044] [Table 1]

[0045]

[0046] As shown in Table 1, when comparing the embodiment and the comparative example, the arithmetic mean roughness Sa is the same as that of the insulator 22, but the Sdr and Spc of the embodiment are larger than those of the comparative example. In addition, when comparing the surface appearance of the insulator 22, the surface of the insulator 22 of the wire 2 of the comparative example has a glossy surface, while the surface of the insulator 22 of the wire 2 of the embodiment has no gloss. Figure 2 As can be seen from (a) and (b), in the embodiment, compared with the comparative example, it can be confirmed that a plurality of fine and sharp concavoconvexities are formed on the surface of the insulator 22. It is believed that the fine concavoconvexities can reduce the contact area when the insulators 22 are brought into contact with each other, thereby reducing friction. It should be noted that in the electric wires 2 of the embodiment and the comparative example, the Shore A hardness of the insulator 22 was measured by the durometer hardness test method (type A) in accordance with JISK 7125, and the result was 89 for the embodiment and 81 for the comparative example. Compared with the comparative example, the hardness of the insulator 22 of the embodiment is slightly higher.

[0047] (Verification of bendability)

[0048] Next, cables 1 of Examples 1 to 3 were produced in which the material of the tape member used in the binding layer 5 and the twisting direction of the electric wires 2 in the core assembly 4 were different, and a flexural test was performed. In the cables 1 of Examples 1 to 3, 42 electric wires 2 of the examples shown in Table 1 were used to form the core assembly 4. In the flexural test, a cable 1 of 300 mm in length was horizontally extended from the end of the base for fixing the cable 1, a predetermined weight was set at the front end of the cable 1, and the deflection amount (i.e., the distance from the base surface to the front end of the cable in the vertical direction) was measured 30 seconds after the start of the test. In Example 1, a foam tape was used in the binding layer 5, and the twisting direction of the electric wires 2 in each layer of the core assembly 4 was set to the same direction. In Example 2, a foam tape was used in the binding layer 5, and the twisting direction of the electric wires 2 in the core assembly 4 was set to different directions in adjacent layers (alternating between each layer). In Example 3, a non-woven fabric tape was used in the binding layer 5, and the twisting direction of the electric wires 2 in each layer of the core assembly 4 was set to the same direction. In addition, 42 wires 2 of the comparative example shown in Table 1 were used to form the core assembly 4. As in Example 3, a nonwoven tape was used in the binding layer 5 to prepare a cable in which the twisting directions of the wires 2 in each layer of the core assembly 4 were set to the same direction. The flexural test was performed in the same manner as in Examples 1 to 3. The results are summarized in Figure 3 .

[0049] like Figure 3As shown, in Examples 1 to 3 of the present invention, the bending amount is larger than that of the comparative example, and it is easier to bend. In addition, it can be confirmed that the bending amount is larger in Examples 1 and 2 using the foam tape in the bonding layer 5 than in Example 3 using the nonwoven fabric tape in the bonding layer 5, and it is easier to bend by using the foam tape in the bonding layer 5. Furthermore, when Example 1 is compared with Example 2, it can be confirmed that when the twisting direction of the electric wires 2 in the collective core 4 is the same in all layers, it is easier to bend and easier to maintain the bent state.

[0050] (Functions and Effects of Implementation Methods)

[0051] As described above, in the cable 1 of the present embodiment, the surface roughness Sdr of the insulator 22 constituting the electric wire 2 is 1.0 or more and the surface roughness Spc is 3000 mm. -1 As a result, the contact area of ​​the contacting parts of the electric wires 2 (i.e., the contacting parts of the surfaces of the insulators 22) is reduced, and the friction force is reduced, so that even if a relatively soft insulator 22 is used, the electric wires 2 can easily move relative to each other in the longitudinal direction. As a result, even in a multi-core cable 1 in which a plurality of electric wires 2 are arranged in close contact, it is easy to bend and maintain the shape in a bent state.

[0052] (Summary of Implementation Methods)

[0053] Next, the technical ideas grasped from the above-described embodiments are described by citing the symbols in the embodiments. However, the symbols in the following description do not limit the constituent elements in the claims to the members specifically shown in the embodiments.

[0054] [1] A cable (1) comprising a plurality of electric wires (2) having an insulator (22) covering the periphery of a conductor (21), and a sheath (7) covering the periphery of a core assembly (4) formed by twisting the plurality of electric wires (2) in two or more layers, wherein the adjacent electric wires (2) in the core assembly (4) are in contact with each other on the surface of the insulator (22), and the surface roughness Sdr of the insulator (22) is not less than 1.0 and the surface roughness Spc is 3000 mm. -1 above.

[0055] [2] The cable (1) according to [1], wherein the insulator (22) has a Shore A hardness of 77 or more and 93 or less.

[0056] [3] The cable (1) according to [1], wherein a bonding layer (5) is provided between the collective core (4) and the sheath (7), and the bonding layer (5) is formed by winding a foaming tape or a non-woven fabric tape having a foaming layer composed of a foamed resin around the collective core (4).

[0057] [4] The cable (1) according to [1], wherein the twisting direction of the plurality of electric wires (2) constituting the collective core (4) is the same in all layers.

[0058] [5] The cable (1) according to [1], wherein the aggregate core (4) is formed by twisting two or more layers of the plurality of electric wires (2) around a central intervening member (3) provided at the center of the cable.

[0059] (Note)

[0060] The embodiments of the present invention are described above, but the embodiments described above do not limit the invention involved in the claims. In addition, it should be noted that all combinations of the features described in the embodiments are not necessary for the method of solving the invention problem. In addition, the present invention can be implemented by appropriately deforming it within the scope of its purpose.

Claims

1. A cable comprising: a plurality of electrical wires having insulation surrounding the conductors; and a sheath covering the periphery of a core assembly formed by twisting the plurality of electric wires in two or more layers, The adjacent electric wires in the collective core are in contact with each other on the surface of the insulator. The surface roughness Sdr of the insulator is greater than 1.0 and the surface roughness Spc is 3000 mm -1 above.

2. The cable according to claim 1, wherein The insulator has a Shore A hardness of 77 or more and 93 or less.

3. The cable according to claim 1, wherein A bonding layer is provided between the collective core and the sheath, The tie layer is formed by winding a foam tape or a nonwoven fabric tape around the assembly core, the foam tape having a foam layer formed of a foaming resin.

4. The cable according to claim 1, wherein The twisting direction of the plurality of electric wires constituting the collective core is the same direction in all layers.

5. The cable according to claim 1, wherein The aggregate core is formed by twisting the plurality of electric wires in two or more layers around a central intervening member provided at the center of the cable.

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